Relight without re-rendering: How Light Mix works in V-Ray 5

Light Mix lets you change the color and intensity of your lights after you’ve rendered your scene. Learn how it works in the new V-Ray Frame Buffer in V-Ray 5.

V-Ray 5 introduces new tools and a new look to the V-Ray Frame Buffer (VFB). In addition to its new icons, cleaner design and improved layout, you’ll notice two key new features on the right side of the interface — Layer Compositing and Light Mix. For this article, we’ll focus on how easy it is to relight a scene with Light Mix in V-Ray 5 for 3ds Max.

With Light Mix in V-Ray 5, you can manipulate your lighting after rendering.

A bit of history

Imagine a scene lit by three lights: a key, fill and rim light. If you render a single image with all three lights turned on, or you render three separate images — one for each light source — and add them back together in compositing, the results are the same. Light is additive.

Enter ray tracing. With ray tracing, it’s possible to track the entire contribution each light has on a rendered scene: diffuse, specular, reflection, refraction and global illumination. When you combine this advantage of ray tracing with the additive nature of light, we can adjust the color and intensity of lights — even after they’ve been rendered.

Technically, V-Ray has had the ability to mix lights ever since the Light Select Render Element was introduced. And this previously required manual setup for each light (or group of lights), plus a trip to a compositing application to make the adjustments.

Wouldn’t it be easier if we could do all this inside the new V-Ray Frame Buffer?

You can quickly and easily rebalance the color and intensity of your lights after rendering with Light Mix.

How to use Light Mix in the new VFB

One of the cool things about the new VFB in V-Ray 5 is that it basically adds lightweight compositing and image-editing capabilities. This means that it can essentially take our Light Selects, as outlined above, and organize them for you. Then you can manipulate the lighting the way you want it — on the fly.

Here is how to manipulate your lighting using the Light Mix in V-Ray 5:

1. First, add the VRayLightMix Render Element. Then select how you would like your lights grouped — individual, instanced, groups or layers.

2. When you hit Render, V-Ray will automatically create the render elements for you — saving you the time of setting them up manually.

3. When the render is finished, you’ll see a list of layers on the right side of the VFB in the compositing section. Select the bottom layer: Source.

4. With the Source layer selected, choose Light Mix from the three modes. You’ll see all lights (or groups of lights) listed with their multiplier, color and on/off switch. Now you can tweak the lights however you want.

5. Once you’re done, you have a few options:

Save the image as is.

Send your Light Mix “To Composite” to break them into layers for compositing.

Push the new values “To Scene” and re-render (this is especially helpful if you notice noise or artifacts from pushing the Light Mix too far).

Try V-Ray 5 for 3ds Max

Download the free public beta and experiment with Light Mix yourself

A few Light Mix examples

To see Light Mix in action, let’s look at an example from The Golden Sheats House (AKA The Big Lebowski house) by one of our favorite artists, Bertrand Benoit. There are several light zones in his scene — which makes it perfect for exploring a variety of lighting options.

Example A

Let's take a look at the first example. Use the sliders to compare the original with the Light Mix — the settings can be seen on the right for each.

How to get the most from Light Mix

Here are some helpful tips to help you set up your scene and work with Light Mix in V-Ray 5.

Organize your lights

If you have a lot of lights in your scene, you’ll want to keep them organized by instances, groups or layers. One of the best ways is to organize them as you would in real life — by switches or circuit breakers.

Make lights bright

Make sure lights are bright enough to easily see their contribution to the scene. Even if you want them to be dim, you can dim them later. In Light Mix, it’s cleaner to dim a light than it is to brighten it. That’s because brightening a light source after you render — especially if you turn it up a lot — can show more grain. So start out with a render that’s nice and bright and then dim it down to 1%, if that’s the effect you want.

Color your lights white

Keeping your light colors neutral white or gray makes them easier to adjust in the Light Mix. It may not be feasible to do this every time, but it’s helpful when you can.

Using Light Mix with Chaos Cloud

If you want to render several scenes at once and mix the lighting afterwards, it’s no problem. One of the easiest ways to do this is to set up your renders as outlined above and render to the Chaos Cloud. Once the EXR is finished, you can load it into the VFB, call up the Light Mix render element, and make your adjustments.

If you have the scene open locally, you push your changes “To Scene” to update it. And you can even send it back to Chaos Cloud to render again.

Light Mix one, fix many

Your Light Mix recipe can be saved as a file and reloaded, in case you’d like to reuse the same values across multiple shots.

Like switching to smart bulbs

The new Light Mix is like switching all the lights in your house to smart bulbs. Instead of running around from room to room turning lights on and off, you can simply adjust everything right from your phone — or in this case from the new V-Ray 5 VFB. Now, you can get your lighting just right even after you’ve rendered — all from the comfort of your couch.

About the author

Chris is a CG industry veteran and Director of Chaos Group Labs. He can also be heard regularly as the host of the CG Garage podcast which attracts 20,000 weekly listeners. With a background in both VFX and Design, Chris has worked for Gensler, Digital Domain, Imageworks and Method Studios. His credits include Maleficent, Oblivion and Tron: Legacy.